The objective of this study is to evaluate the safety, tolerability, and effectiveness of adefovir dipivoxil in adult patients diagnosed with chronic hepatitis B virus (HBV). Currently, the standard of care for patients with HBV is controversial. The only FDA approved therapy at this time is interferon, and this on the condition that the patient tests positive for the E-antigen and does not have advanced liver disease. Thus, further research into treatments for this disease is needed, including studies that will compare the treatment to placebo, such as this one. Once a patient has been determined eligible for participation in a protocol for adefovir dipivoxil treatment, he or she will be assigned by chance to one of six different study groups for Study Year 1 and Study Year 2. Even though this is a placebo-controlled study, all patients enrolled in the study will be assigned to receive at least one year of adefovir dipivoxil treatment during this two-year study. For Study Year 2, some of the patients will continue with the same treatment and others will receive a different treatment from Study Year 1. After the initial visit in Study Year 1, patients will return to the clinic every fourth week. The length of treatment in the study will last for 24 months (or until patient withdraws or is removed from the study for some reason), followed by a 1-month follow-up period.